When fabricating conductive features in a semiconductor, a chlorine (Cl) residue may remain on the surfaces of the metal stacks from which the features are formed, as illustrated in FIGS. 1 and 1a. As a result, voids or pits in the feature tend to result upon processing the metal through a heat step, such as an alloy step. The pitting has been especially noticeable in metal layers comprising titanium, for example, an aluminum (Al), titanium (Ti), and copper (Cu) stack. Such a stack may be used in the fabrication of metal interconnects, buses, vias, etc. This problem has been described in "A Novel Via Failure Mechanism in an Al-Cu/Ti Double Metal Level System," by Freiberger and Wu.
Current approaches to the above stated problem involve the use of a chromic phosphoric acid solution on the metal surfaces. While this material is somewhat effective in solving the problem, chromic phosphoric acid is highly carcinogenic, and therefore requires special handling during use and disposal. Thus, alternative solutions are being sought by the industry.
Another problem exists with regard to metallization process in bond pad formation. Aluminum is a metal with a very high chemical reactivity. Unfortunately, certain oxide layers interfere with the efficient functioning of the semiconductor device.
During the metal patterning step the aluminum bond pads are defined and etched. Subsequently, a passivation layer is deposited on the device to protect the device throughout the testing and packaging processes. However, the protective layer is first removed from the conductive bond pads through a pad mask patterning step. The pad mask step is typically done in a plasma or dry etch chamber.
After a semiconductor device has undergone the pad mask step, residual fluorine may remain on the bond pads from the etch chemicals, for example CHF.sub.3, used in the process. This fluorine residue causes a condition referred to as "gummy pads" which is characterized by an adhesive-like oxide substance remaining on the bond pads (as illustrated in FIG. 5), which substance clings to the probe tips during die testing.
The "gummy bond pads" arise because the silicon nitride layer superjacent the aluminum bond pads is typically overetched. Fluorine (F) from the etch process is deposited onto the aluminum of the bond pads, producing an AlFO.sub.3 oxide layer on the bond pads. The fluorine acts as an oxidizing agent which creates a greater than normal layer of oxide, thereby resulting in high resistivity, and consequently, low yields when probed.